1. Field of the Invention
The present invention relates to a damping material excellent in damping properties which can be used as a sound insulation material or damping material for driver in data recording electronic apparatus.
The present invention also relates to a damping method which can minimize vibration developed by the rotational driving of a disc to exert a high sound-insulating or damping effect and thus is suitable for the formation of drive for data recording disc and a disc drive comprising a damping material.
The present application is based on Japanese Patent Applications No. Hei. 10-253258, 10-267466 and 10-267467 which are incorporated herein by reference.
2. Description of the Related Art
Damping materials which absorb or reflect vibration to perform sound insulation or damping have been used for various purposes such as sound insulation, sound absorption, damping, composite thereof, etc.
HDD (hard disc drive), DVDD (digital video disc drive), CDD (compact disc drive), MOD (MO drive), FDD (floppy disc drive), etc. in personal computers comprise a damping material provided in various places, e.g., between the drive main body and the substrate to prevent the generation of noise such as skirr during the rotational driving of a disc as a magnetic or optical data recording medium or the propagation of the motor vibration.
As the foregoing damping material there has heretofore been known a foamed product made of a polyurethane foam or the like. However, if this foamed product is used as a sound insulation material, it is disadvantageous in that there occurs much sound leakage, exerting a reduced sound insulating effect. Therefore, a foamed product having a specified static spring constant, a damping material obtained by forming a finely roughened polymer film on the inner wall of cells in a foamed product, a foamed product having a film applied to the external surface thereof, and a film laminated with a melt blow layer of resin have been proposed (Japanese Patent Publications Sho. 56-157347, Sho. 59-102294, Hei. 4-40381, Hei. 4-345834 and Hei. 7-261768).
However, all the conventional damping materials are disadvantageous in that they exert a poor damping effect and, if used as a sound insulation material, exert an insufficient sound insulating effect or sound deafening effect, making it impossible to prevent the generation of noise. The damping material having a finely roughened polymer film formed thereon, etc. is disadvantageous in that it requires a complicated production process and is produced at a poor production efficiency.
Further, all the conventional disc drives are disadvantageous in that the damping material incorporated therein exerts a poor damping effect and thus exerts a poor effect of deafening sound by sound insulation, sound absorption or damping or a poor effect of inhibiting the propagation of vibration, causing much noise leakage or read/write error.
It is an object of the present invention to develop a damping material excellent in damping properties which can exert a high effect of insulating from sound or damping, can be easily used in a narrow space, can be produced at a good efficiency and can be used for various purposes such as sound insulation and damping.
It is another object of the present invention to provide a damping method which can exert an excellent damping effect to perform high sound insulation or damping and can be easily used in a narrow space or the like and hence provide a disc drive which generates no noise leakage or read/write error.
It is still another object of the present invention to provide a damping material made of a porous member having an absolute characteristic impedance value of not less than 800 kg/m2xc2x7S in the frequency range of from 1.0 to 3.0 kHz.
The damping material according to the present invention can be produced at a high efficiency. The porous member which exhibits the above defined impedance characteristics can exert an excellent effect of minimizing vibrations such as sound incident thereupon. Accordingly, a damping material can be obtained which exerts an excellent sound deafening effect or damping effect to perform high noise prevention or damping and thus can be used for various purposes such as sound insulation, sound absorption, damping and composite thereof. A compressible porous member, if used as a damping material, can be easily loaded in a narrow space or the like, making it possible to prevent the increase of the entire size of the apparatus due to the increase of the thickness of the damping material.
In the foregoing description, if the damping material exhibits a damping factor a satisfying the relationships xcex1xe2x89xa70.01 f neper/m, supposing that the frequency is f, it can exert a drastically enhanced effect of deafening sound or damping to perform further noise prevention or damping. Further, a porous member which exhibits a repulsion stress of from 10 to 200gf/cm2 at 50% compression, if used as a damping material, can be more easily loaded in a narrow space or the like without deforming the adjacent members and can be easily produced.
The present invention also provides a damping method which comprises providing a damping material in the interior or on the periphery of a vibration-generating apparatus, characterized in that as said damping material there is used a compressible porous member having an air permeability of from 1xc3x97{fraction (1/10)}10to 2xc3x97{fraction (1/10)}2cc/cm2/sec based on an atmospheric pressure difference of 2.039xc3x97{fraction (1/10)}4 mmH2O or a porous member having an absolute impedance value of not less than 800 kg/m2xc2x7S in a frequency range of from 1 to 3 kHz.
The present invention further provides a disc drive comprising a motor for rotating a disc as a data recording medium and a damping material provided in the interior and/or on the periphery of a housing having at least a space in which said disc can be mounted, characterized in that said damping material is made of a compressible porous member having an air permeability of from 1xc3x97{fraction (1/10)}10 to 2xc3x97{fraction (1/10)}2 cc/cm2/sec based on an atmospheric pressure difference of 2.039xc3x97{fraction (1/10)}4 mmH2O or a porous member having an absolute impedance value of not less than 800 kg/m2xc2x7S in a frequency range of from 1 to 3 kHz.
In accordance with the present invention, the porous member constituting the damping material exhibits excellent damping properties based on the foregoing air permeability and impedance characteristics to exert a high sound deafening or damping effect developed by sound insulation, sound absorption and damping, making it possible to perform excellent noise prevention or damping for vibration-generating apparatus such as disc drive. Further, the damping material made of a porous member can be produced at a high efficiency and can be easily mounted in a narrow space or the like, making it possible to prevent the increase of the entire size of the apparatus due to the increase of the thickness of the damping material.
In the foregoing description, if the damping material is made of a porous member having a sound absorbing coefficient of not less than 20% at a frequency of 3.15 kHz or a damping factor of not less than 0.01 f neper/m where f is frequency at a frequency of 3.15 kHz, the resulting sound deafening effect or damping effect is drastically enhanced, making it possible to perform better noise prevention or damping. Further, the damping material, if made of a porous member having a repulsion stress of from 10 to 200 gf/cm2 at 50% compression, can be more easily mounted in a narrow space without deforming the adjacent members. Such a damping material can also be easily produced.
Still further, the present invention provides a damping method which comprises providing a damping material in the interior or on the periphery of a vibration-generating apparatus, characterized in that as said damping material there is used one obtained by forming a film layer on a compressible porous member having an air permeability of from 1xc3x97{fraction (1/10)}10 to 2xc3x97{fraction (1/10)}2cc/cm2/sec based on an atmospheric pressure difference of 2.039xc3x97{fraction (1/10)}4 mmH2O or one obtained by forming a film layer on a porous member having an absolute impedance value of not less than 800 kg/m2xc2x7S in a frequency range of from 1 to 3 kHz.
The present invention also provides a disc drive comprising a motor for rotating a disc as a data recording medium and a damping material provided in the interior and/or on the periphery of a housing having at least a space in which said disc can be mounted, characterized in that said damping material is made of a material obtained by forming a film layer on a compressible porous member having an air permeability of from 1xc3x97{fraction (1/10)}10 to 2xc3x97{fraction (1/10)}2 cc/cm2/sec based on an atmospheric pressure difference of 2.039xc3x97{fraction (1/10)}4 mmH2O or a material obtained by forming a film layer on a porous member having an absolute impedance value of not less than 800 kg/m2xc2x7S in a frequency range of from 1 to 3 kHz.
In accordance with the present invention, the damping material is formed by a porous member showing the foregoing air permeability and impedance characteristics to exert an excellent damping effect. Further, the damping material comprises a film layer formed thereon to exert an excellent effect of insulating from sound or preventing the propagation of vibration. Thus, a high sound deafening or damping effect developed by sound insulation, sound absorption and damping can be exerted, making it possible to perform excellent noise prevention or damping for vibration-generating apparatus such as disc drive.
Further, the damping material made of porous member and film layer can be produced at a high efficiency. The damping material reinforced by the film layer can be more fairly handled and thus can be fairly mounted in the apparatus, making it possible to inhibit the scattering of properties such as sound insulation and damping. Thus, the stability and reliability in prevention of noise, vibration, etc. can be enhanced. Further, the damping material can be easily mounted in a narrow space, making it possible to inhibit the increase of the entire size of the apparatus due to the increase of the thickness of the damping material.
In the foregoing description, if the damping material is made of a porous member having a sound absorbing coefficient of not less than 20% at a frequency of 3.15 kHz and a damping factor xcex1 satisfying the relationship: xcex1xe2x89xa70.01 f neper/m, supposing that the frequency is f, it can exert a drastically enhanced effect of deafening from sound or damping to perform further noise prevention or damping. Further, a porous member which exhibits a repulsion stress of from 10 to 200 gf/cm2 at 50% compression, if used as a damping material, can be more easily loaded in a narrow space or the like without deforming the adjacent members and can be easily produced.
Features and advantages of the invention will become understood from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.